Grafted and cross-linked epm

Abstract

The peroxide catalyzed reaction of maleic anhydride and a saturated ethylene-propylene rubber of low molecular weight and the hydrolysis thereof produces a reversibly crosslinked product of apparent higher molecular weight by measure of Mooney viscosity but apparent unchanged molecular weight by reduced solution viscosity (RSV). The graft product of a low molecular weight semi-solid substrate can be recovered conveniently as a non-cold flowing solid which has utility as a low molecular weight oil VI improver and as an impact modifier for polar thermoplastic resins.

I claim: 
     
       1. A grafted and reversibly crosslinked, ethylene, mono-olefin copolymer having an RSV value within the range of 0.4 to 3.0 and in which the copolymer is a polymer rubber which is free of unsaturated carbon to carbon linkages in the polymer chain, in which the material grafted onto the polymer is an anhydride or derivative thereof having the general formula: ##STR3## or correspondening dicarboxylic acid or derivative thereof having the general formula: ##STR4## in which R is an alkylene group having from 0 to 4 carbon atoms, Y is selected from the group consisting of hydrogen, halogen or an organic group having from 1-12 carbon atoms and X is a hydroxyl or ester forming group but in which at least one X is hydroxyl, and in which the crosslinks are formed in the presence of water and are easily disruptable in use whereby the grafted and crosslinked polymer comprises a solid high molecular weight material which reverts to a low molecular weight in use. 
     
     
       2. A grafted and reversibly crosslinked polymer as claimed in claim 1, in which the polymer is formed by copolymerization of ethylene and one or more higher mono-olefins. 
     
     
       3. A grafted and reversibly crosslinked polymer as claimed in claim 1, in which the polymer is a copolymer of ethylene and propylene. 
     
     
       4. A grafted and reversibly crosslinked EPM as claimed in claim 3, in which the mono-olefins are present in EPM in the ratio of 95-10 moles of ethylene to 5-90 moles of propylene. 
     
     
       5. A grafted and reversibly crosslinked EPM as claimed in claim 3, in which the mono-olefins are present in EPM in the ratio of 40-66 moles of ethylene to 60-34 moles of propylene. 
     
     
       6. A grafted and reversibly crosslinked EPM are claimed in claim 3, in which the material grafted onto the EPM is maleic anhydride. 
     
     
       7. A grafted and reversibly crosslinked EPM as claimed in claim 3, in which the material grafted onto the EPM is maleic acid or mono ester thereof. 
     
     
       8. A grafted and reversibly crosslinked EPM as claimed in claim 3, in which the amount of graft is within the range of 0.5 to 4%. 
     
     
       9. A grafted and reversibly crosslinked EPM as claimed in claim 3, in which the amount of graft is within the range of 0.2 to 5%. 
     
     
       10. A grafted and reversibly crosslinked EPM as claimed in claim 3, in which the EPM is a liquid or semi-liquid or coldflowing EPM having an RSV within the range of 0.7 to 2.5. 
     
     
       11. A grafted and reversibly crosslinked EPM as claimed in claim 3, in which the crosslinks are disruptable when heated to a temperature above 125° in use. 
     
     
       12. A grafted and reversibly crosslinked EPM as claimed in claim 3, in which the crosslinks are disruptable when treated with an alcohol. 
     
     
       13. The method for producing a grafted and reversibly crosslinked polymer as claimed in claim 1, which comprises the steps of grafting onto a low molecular weight polymer free of unsaturated groups in the polymer chain, an anhydride or derivative thereof having the general formula: ##STR5## or its corresponding dicarboxylic acid or derivative thereof having the general formula: ##STR6## in which R is an alkylene group having from 0 to 4 carbon atoms, Y is selected from the group consisting of hydrogen, halogen or an organic group and X is a hydroxyl or ester forming group in which at last one X is hydroxyl, and crosslinking the grafted polymer in the presence of water whereby crosslinks that are formed are of the labile type to provide a solid high molecular weight grafted and crosslinked polymer but in which the crosslinks are easily disrupted in use to provide a low molecular weight grafted polymer. 
     
     
       14. The method as claimed in claim 13, in which the polymer is a polymer formed by copolymerization of ethylene and one or more higher mono-olefins. 
     
     
       15. The method as claimed in claim 13, in which the polymer is a copolymer of ethylene and propylene. 
     
     
       16. The method as claimed in claim 13, in which the polymer is an EPM copolymer of ethylene and propylene present in the EPM in the ratio of 95-10 moles of ethylene to 5-90 moles of propylene. 
     
     
       17. The method as claimed in claim 15, in which the mono-olefins are present in the EPM in the ratio of 40-66 moles of ethylene to 60-34 moles of propylene. 
     
     
       18. The method as claimed in claim 15, in which the material grafted onto the EPM is maleic anhydride. 
     
     
       19. The method as claimed in claim 15, in which the material grafted onto the EPM is maleic acid or a mono ester thereof. 
     
     
       20. The method as claimed in claim 15, in which the amount of graft is within the range of 0.5 to 4%. 
     
     
       21. The method as claimed in claim 15, in which the amount of graft is within the range of 0.2 to 5%. 
     
     
       22. The method as claimed in claim 15, in which the EPM is a liquid or semi-liquid or coldflowing EPM having an RSV within the range of 0.7 to 2.5. 
     
     
       23. The method as claimed in claim 15, in which the crosslinks are disruptable when heated to a temperature above 125° in use.